#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

int main()
{
    int i, j;
    int x = 0;
    int y = 5;
    int velocity_x = 1;
    int velocity_y = 1;
    int left = 0;
    int right = 20;
    int top = 0;
    int bottom = 10;

    while(1)
    {
        x = x + velocity_x;
        y = y + velocity_y;
        //清屏函数
        system("cls");
        //输出小球上面的空行
        for(i = 0; i < x; i++)
        {
            printf("\n");
        }
        //输出小球左边的空格
        for(j = 0; j < y; j++)
        {
            printf(" ");
        }
        //输出小球
        printf("o");
        printf("\n");
        //等待若干毫秒
        Sleep(50);

        if((x==top) || (x==bottom))
            velocity_x = -velocity_x;
        if((y==left) || (y==right))
            velocity_y = -velocity_y;
    }

    return 0;
}
